Demonstration of two-tier sorting using comparators

#!/usr/bin/env python2
# https://repl.it/@BradenBest/ProbableJuvenileRegisters

# Defining a general-purpose sort function (selection sort algorithm)
# function takes a list and an optional comparator

def cmp_default(a, b):
    """General purpose comparator. Works for numbers and strings"""
    if(a < b): return -1
    if(a > b): return 1
    return 0

def swap(array, a, b):
    temp = array[a]
    array[a] = array[b]
    array[b] = temp

def sort_run(array, start, cmp):
    """find the lowest item and swap it with the start point"""
    lowest = start

    for i in xrange(start, len(array)):
        if cmp(array[lowest], array[i]) > 0:
            lowest = i

    if lowest != start:
        swap(array, start, lowest)

def sort(array, cmp = cmp_default):
    for i in xrange(len(array)):
        sort_run(array, i, cmp)

# Testing our sort function

def cmp_flight(a, b):
    """Sort by destination first, arrival time second"""
    cmpr = cmp_default(a[0], b[0])

    if cmpr == 0:
        return cmp_default(a[1], b[1])

    return cmpr

def before_and_after(lst, cmp = None):
    print "Before: %s" % str(lst)

    if cmp is None:
        sort(lst)
    else:
        sort(lst, cmp)

    print "After:  %s\n" % str(lst)

list1 = [1,5,32,6,7,2,7,34,6,8,34,9,5,1,454,2]
list2 = ["Alice", "Xander", "Jerry", "Bob", "Bobert", "Ian"]
list3 = [["Chicago", 1045], ["Birmingham", 630], ["Chicago", 700], ["Birmingham", 845]]

before_and_after(list1)
before_and_after(list2)
before_and_after(list3, cmp_flight)